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arXiv 2103.03035cs.DS
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基于叶子的子集反馈顶点集计算

Computing Subset Feedback Vertex Set via Leafage

Charis Papadopoulos, Spyridon Tzimas

摘要:

在弦图的子类中表现出计算上不同的一个典型例子是\textsc{Subset Feedback Vertex Set}(SFVS)问题:给定顶点加权图$G=(V,E)$和集合$S\subseteq V$,\textsc{Subset Feedback Vertex Set}(SFVS)问题要求与包含$S$的顶点的所有圈相交的最小权重的顶点集合。已知SFVS在区间图上是多项式时间可解的,而SFVS在分裂图上保持\NP -完全,因此在弦图上也是如此。为了更好地理解弦图子类上SFVS的复杂性,我们利用树模型的结构特性,以应付SFVS的硬度。在这里,我们考虑的\emph{leafage},测量树模型中的最小数量的叶子的变体。我们表明,SFVS可以解决在多项式时间内的每一个弦图有界叶。特别是,给定一个弦图的$n$顶点与叶$\ell$,我们提供了一个算法SFVS与运行时间$n^{O(\ell)}$。我们通过证明SFVS是由$\ell$参数化的\W [1]-hard来补充我们的结果。进一步推进我们的积极结果,很自然地考虑叶龄的轻微推广,\emph{vertex leafage},它测量树模型中所有子树的最大叶数中的最小数。然而,我们表明,这是不可能获得类似的结果,因为我们证明,SFVS仍然\NP -完全无向路径图,即,顶点叶数至多为2的图。此外,我们加强了以前已知的多项式时间算法SFVS根路径图,形成一个适当的子类的无向路径图和图的最小宽度。

英文摘要:

A typical example that behaves computationally different in subclasses of chordal graphs is the \textsc{Subset Feedback Vertex Set} (SFVS) problem: given a vertex-weighted graph $G=(V,E)$ and a set $S\subseteq V$, the \textsc{Subset Feedback Vertex Set} (SFVS) problem asks for a vertex set of minimum weight that intersects all cycles containing a vertex of $S$. SFVS is known to be polynomial-time solvable on interval graphs, whereas SFVS remains \NP-complete on split graphs and, consequently, on chordal graphs. Towards a better understanding of the complexity of SFVS on subclasses of chordal graphs, we exploit structural properties of a tree model in order to cope with the hardness of SFVS. Here we consider variants of the \emph{leafage} that measures the minimum number of leaves in a tree model. We show that SFVS can be solved in polynomial time for every chordal graph with bounded leafage. In particular, given a chordal graph on $n$ vertices with leafage $\ell$, we provide an algorithm for SFVS with running time $n^{O(\ell)}$. We complement our result by showing that SFVS is \W[1]-hard parameterized by $\ell$. Pushing further our positive result, it is natural to consider a slight generalization of leafage, the \emph{vertex leafage}, which measures the smallest number among the maximum number of leaves of all subtrees in a tree model. However, we show that it is unlikely to obtain a similar result, as we prove that SFVS remains \NP-complete on undirected path graphs, i.e., graphs having vertex leafage at most two. Moreover, we strengthen previously-known polynomial-time algorithm for SFVS on rooted path graphs that form a proper subclass of undirected path graphs and graphs of mim-width one.

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